The treatment of human hair to alter its appearance, including its color and shape, has long been an objective of the hair care industry. In order for such treatments to be considered successful, especially for treatments in vivo, varied and sometimes contradictory requirements must be satisfied. For example, the capability of precisely producing the desired degree of shape alteration is of primary importance for all hair perming and straightening techniques. However, the ability to fully achieve this objective has heretofore frequently been limited by countervailing requirements. For example, treatments must be effectively completed in the shortest possible period of time in order to be acceptable to the person undergoing the treatment; yet, longer treatment times have heretofore sometimes been required to achieve the desired degree of shape alteration. On the other hand, longer treatment times tend to produce hair damage and offensive skin and/or scalp irritation.
It has heretofore been common practice to treat kinky or curly hair with highly alkaline or caustic aqueous solutions in an effort to soften or reduce the natural elasticity or resiliency of the hair. While the use of such solutions has been partially effective, there are many serious disadvantages as well. For example, methods employing such compositions usually require that the hair and scalp be exposed to highly caustic conditions (e.g.: pH of about 12 to 14) for extended periods of time (e.g.: 45 minutes). Such exposure has heretofore frequently caused a permanent deleterious effect on the aesthetic and structural qualities of the hair and has been known to frequently cause severe irritation or burning of the scalp. See, for example, the article by F. Lewis, M. D., in the Journal of the American Medical Association, Jan. 7, 1939. Moreover, such compositions usually have a very unpleasant odor and are uncomfortable to the person whose hair is being treated. Moreover, it is difficult or impossible to alleviate such offensive odors by traditional methods, such as including a pleasant fragrancing agent in the solution since the compounds of the fragrance are usually destroyed or rendered ineffective in highly caustic solutions. It also appears that such compositions have heretofore caused changes in the structure of the hair which preclude further beneficial chemical treatment of the hair, such as coloring. For example, hair treatment compositions containing sodium or potassium hydroxide, especially at high concentrations of active ingredient, can cause rupture of various linkages and bonds in the protein molecules of the hair to an extent that damage to and embrittlement of the hair occur. For this reason, all heretofore used compositions of this type have required the use of a protective cream which is applied to the scalp and surrounding epidermis prior to application of the shape altering composition. See Wall, F. E., "Hair Straighteners," Cosmetics: Science and Technology, Vol. 2, 2nd ed., John Wiley & Sons, p. 265 (1972).
Methods are also currently available for imparting a so-called "permanent wave" to hair which is naturally relatively straight. One frequently used method requires application of a highly alkaline solution to the hair and subsequent physical curling of the hair in the presence of heat. See for example U.S. Pat. No. 2,115,156--Brown. In addition to the disadvantages described above in connection with the use of highly caustic solutions, another problem with such methods is that they require the use of high heat in close proximity to the skin and scalp, creating the potential for severe burning.
Methods also exist for imparting a permanent wave to hair without the application of heat. Such methods generally require the application of a highly alkaline softening composition to the hair, followed by mechanically conforming the hair to the desired shape. An acidic fixing composition is then applied directly to the conformed and softened hair. The fixing composition neutralizes the softening composition and is said to restore the natural elasticity to the hair. An example of such a method is described in U.S. Pat. No. 2,061,709--Malone. Once again, these methods suffer from all the disadvantages associated with the application of a highly caustic composition to the hair. Moreover, it is difficult if not impossible, to apply the exact amount of acidic fixing composition required to completely neutralize the softening composition without leaving the hair in a slightly acid condition, which in turn will result in an undesirable further softening of the hair.
Another method which has heretofore been used for the treatment of hair includes mixing cysteine in powder or crystalline form to a treating solution just prior to application of the solution to the hair. The treating solution of such heretofore used methods generally comprised sodium hydroxide solutions having a pH of about 12. Of course, such caustic solutions suffer from all the disadvantages described above, such as the scalp burning and hair damage which may result from the use thereof. Moreover and just as importantly, cysteine is unstable in aqueous solution and is readily oxidized by dissolved oxygen, thereby precluding long-term storage of the heretofore used solutions. Another disadvantage is that such methods are cumbersome, inconvenient and may result in an improperly formulated treating solution. It also is relatively expensive to separately and anaerobically package an accurately defined amount of cysteine powder, as would be required to prevent oxidation or decomposition.
More recently, as disclosed in above-listed U.S. Pat. Nos. 4,947,878, 5,101,841 and 5,415,856, it has been found that safe, effective methods and compositions for the chemical treatment of hair, and, more particularly, for imparting a permanent wave to hair without the application of substantial heat thereto, or for otherwise altering the configuration of hair while protecting the hair and scalp from the deleterious effects of exposing the hair to highly caustic solutions, as well as stable aqueous solutions containing cysteine or a similar shaping agent for the treatment of hair, are disclosed that employ a hair shaping composition comprising a shaping agent and a disaccharide. According to preferred embodiments disclosed therein, the shaping agent comprises a reducing agent for reducing the hair. According to other preferred embodiments disclosed therein, the shaping agent comprises alkali. Such compositions have been found to provide excellent ability to cause the desired degree of shape alteration while simultaneously protecting the hair and scalp from burning or damage.
According to certain other preferred embodiments thereof, it was found that certain stabilized solutions of cysteine or other shaping agents are effective softening or reducing agents in the treatment of hair. More particularly, it was found that aqueous solutions containing cysteine or another shaping agent and a non-reducing disaccharide are stable and effective compositions for treating hair.
German Offen. DE 3,631,991, discloses a reducing agent composition that is a combination of cysteamine, or its salts, together with a monothioglycolic acid ester for permanent hair waving (see CA Selects: Cosmetic Chemicals, Issue 1, 1989, 109:236730h). Also, the use of an N-acylcysteamine, HSCH.sub.2 CH.sub.2 NH--COR (R-2-10 C alkyl), as a hair reducing compound, together with another reducing agent selected from the group consisting of cysteine, acidic sodium hyposulfite, sodium sulfite, thioglycerol and thiolactic acid is disclosed in Japanese Patent JP 63146808. Also, published European Patent Application 88 306449.5, publication number 0299764, discloses the use of cysteamine as a reducing agent together with sulfite, bisulfite and disulfide compounds, such as cystamine, to effect reoxidation; and the use of cystamine, as an oxidizing agent in the permanent waving process is disclosed in U.S. Pat. No. 4,795,629. Japanese published Patent Application No. 2053-714-A discloses cysteamine together with a dithioglycolate stop action compound.
It has been postulated that the reducing action of mercaptans on keratin is due mostly to the dissociated form of the thiol groups, the thiolate anion. Acid permanent waves sufficiently curl hair at a lower pH compared to alkaline permanents because the waving agents in these permanents have low pKa values and thus exist predominantly in dissociated (thiolate) form at a pH near neutral, or at a slightly acidic pH. Hence, the pKa value shows that some mercaptans are efficient at high pH values while others with a low pKa value and high ionization constant are efficient at lower pH values. For example, it is well known that the alkaline salts of thioglycolic acid, e.g., the ammonium salt of thioglycolic acid (pKa=10.4), have acceptable waving efficiency only if the pH of the solution exceeds 9. See Zviak, Charles, The Science of Hair Care, Permanent Waving and Hair Straightening, p. 191, 1986. On the other hand, amides, such as thioglycolamide (pKa=8.4), and esters, such as glycerol thioglycolate (pKa=7.8), give acceptable waving efficiency at neutral and even slightly acid pH.
Japanese published application No. 55-136857 teaches that cysteamine-based permanent waving compositions are more effective with thioglycolic acid reducing agents. U.S. Pat. No. 5,260,054 discloses a cysteamine-based permanent wave composition, without a thioglycolate or thioglycolic acid, in a single formula which can be applied in a single predetermined amount of time to the hair. According to the disclosure of that patent, regardless of the structure of the hair, whether it be damaged or not, the compositions of the '054 patent are capable of being water wrapped or lotion wrapped without the use of a dryer, hair caps or other heat treatment to speed the reducing agent action. However, such prior art cysteamine-based permanent wave compositions, while having many positive attributes, have an unacceptable malodor associated therewith.